Fix build when libaio-devel is not available
Fix build when libaio-devel is not available

* desc.c: Do not compile code that uses struct iocb unless
HAVE_LIBAIO_H is set.

Reported-by: Denys Vlasenko <50fbbd36fe0f9c8261d4a3c762c8c29ffb35e48f@redhat.com>

AOSP-YU/platform_external_strace,pgbovine/strace-plus,bnoordhuis/strace,bigzz/strace_android,jamel/strace-plus,CyanogenMod/android_external_strace,Saruta/strace,lkundrak/strace,geekboxzone/mmallow_external_strace,AOSP-YU/platform_external_strace,bigzz/strace_android,pombredanne/strace,TeamExodus/external_strace,cuviper/strace,CyanogenMod/android_external_strace,CyanogenMod/android_external_strace,kapdop/android_external_strace,MonkeyZZZZ/platform_external_strace,gcode-mirror/strace-plus,Infinitive-OS/platform_external_strace,DirtyUnicorns/android_external_strace,Yu-AndroidM/android_external_strace,android-ia/platform_external_strace,vrastogi/strace,gcode-mirror/strace-plus,Distrotech/strace,kapdop/android_external_strace,gcode-mirror/strace-plus,jamel/strace-plus,vrastogi/strace,xin3liang/platform_external_strace,pombredanne/strace,DirtyUnicorns/android_external_strace,DirtyUnicorns/android_external_strace,MonkeyZZZZ/platform_external_strace,Saruta/strace,pgbovine/strace-plus,Andrey9kin/revisor,lkundrak/strace,MonkeyZZZZ/platform_external_strace,vrastogi/strace,Distrotech/strace,Saruta/strace,android-ia/platform_external_strace,Yu-AndroidM/android_external_strace,pombredanne/strace,Infinitive-OS/platform_external_strace,geofft/strace,geekboxzone/lollipop_external_strace,TeamExodus/external_strace,android-ia/platform_external_strace,xin3liang/platform_external_strace,bigzz/strace_android,timmattison/strace-arm,Infinitive-OS/platform_external_strace,android-ia/platform_external_strace,xin3liang/platform_external_strace,geekboxzone/mmallow_external_strace,TeamExodus/external_strace,AOSP-YU/platform_external_strace,bnoordhuis/strace,Yu-AndroidM/android_external_strace,android-ia/platform_external_strace,jamel/strace-plus,CyanogenMod/android_external_strace,Yu-AndroidM/android_external_strace,AOSP-YU/platform_external_strace,pgbovine/strace-plus,cuviper/strace,geofft/strace,cuviper/strace,TeamExodus/external_strace,YUPlayGodDev/platform_external_strace,lizh06/strace-plus,cuviper/strace,AOSP-YU/platform_external_strace,geekboxzone/lollipop_external_strace,geofft/strace,kapdop/android_external_strace,YUPlayGodDev/platform_external_strace,vrastogi/strace,Andrey9kin/revisor,DirtyUnicorns/android_external_strace,geekboxzone/mmallow_external_strace,CyanogenMod/android_external_strace,lkundrak/strace,geekboxzone/mmallow_external_strace,geofft/strace,Yu-AndroidM/android_external_strace,DirtyUnicorns/android_external_strace,TeamExodus/external_strace,Saruta/strace,Andrey9kin/revisor,MonkeyZZZZ/platform_external_strace,Saruta/strace,jamel/strace-plus,YUPlayGodDev/platform_external_strace,Distrotech/strace,Andrey9kin/revisor,bnoordhuis/strace,geekboxzone/lollipop_external_strace,bigzz/strace_android,geekboxzone/lollipop_external_strace,pgbovine/strace-plus,MonkeyZZZZ/platform_external_strace,geofft/strace,geekboxzone/lollipop_external_strace,pgbovine/strace-plus,Infinitive-OS/platform_external_strace,cuviper/strace,kapdop/android_external_strace,pombredanne/strace,lizh06/strace-plus,timmattison/strace-arm,kapdop/android_external_strace,gcode-mirror/strace-plus,xin3liang/platform_external_strace,lizh06/strace-plus,lizh06/strace-plus,gcode-mirror/strace-plus,geekboxzone/mmallow_external_strace,vrastogi/strace,timmattison/strace-arm,lkundrak/strace,jamel/strace-plus,Distrotech/strace,lizh06/strace-plus,bigzz/strace_android,Infinitive-OS/platform_external_strace,YUPlayGodDev/platform_external_strace,Distrotech/strace,bnoordhuis/strace,YUPlayGodDev/platform_external_strace